<?php


abstract class Test {
    abstract function t();
    abstract function t1();
}

abstract class Test1 extends Test{
    //abstract 不能被重写
    //abstract function t();
    abstract function t2();
}

class Test2 extends Test1{
    //必须全部实现抽像方法
     function t(){
        echo 't1';
     }
     function t1(){
        echo 't2';
     }
     function t2(){
        echo 't3';
     }
}